1. Field of the Invention
This invention relates to a device for the granulation of a plastic molding compound which does not flow under gravity, more particularly an enzyme concentrate suitable for detergents, comprising a granulating head which adjoins an extruder and which comprises a number of bore-like passages on its outlet side and a preliminary distributor in the form of a perforated plate arranged at a distance from the extruder screw and the bore-like passages on the extruder side.
Modern detergents contain enzyme granules, for example proteases, amylases, lipases. In the production of enzyme granules, it is important to obtain a dust-free product of homogeneous composition and uniform external appearance, including shape, color and general appearance. Since granules of the type in question must not disintegrate in the detergent powder, their particle sizes have to be comparable with the other granules. Accordingly, die plates having bore diameters of less than 0.8 mm have to be used where an extruder is employed for granulation.
Enzyme granules consist not only of the liquid enzyme concentrates, but also of fillers, zeolites, tripolyphosphates, starch, cellulose, methyl cellulose, carboxymethyl cellulose, waxes, water-soluble polymers, etc.
Another problem is the uniform distribution of the compound to be processed over the entire cross-section of the molding plates containing die plates. This problem is particularly serious when the cross-section of the molding plate, for example with 3,000 to 6,000 individual bores, is considerably larger than the cross-section of the outlet opening for the molding compound at the end of the extruder screw. Unless the molding compound to be processed is uniformly distributed over the entire cross-section of the moulding plate, the compound issues from the individual openings at different rates. Accordingly, the issuing strands are cut into granules of different length by the blade rotating in front of the moulding plate so that a uniform product cannot be obtained.
2. Discussion of Related Art
Although a device of the type mentioned at the beginning is known from DE-OS 25 57 166, only a few (about twenty at most) bore-like passages are provided in the known granulating head so that the above-mentioned problem of uniform distribution of the molding compound does not arise. In the known extruder, the molding compound is uniformly distributed for the simple reason that all the bores are arranged symetrically to one another and equidistantly from the central axis of the extruder.
Accordingly, the problem addressed by the present invention was to provide a granulating device of the type mentioned at the beginning which would enable the molding compound for processing to be uniformly distributed over the entire cross-section of the moulding plate even when the cross-section of the moulding plate was considerably larger than the cross-section of the outlet opening for the molding compound at the end of the extruder screw.